Enzymes

Enzymes

  • biological catalysts
  • speed up reactions so that the reactions happen at normal body temperature
  • globular proteins with tertiary or quaternary structure

Substrate

  • reactant
  • 2 substrates forming 1 product or 1 substrate forming 2 products
  • catabolic or anabolic metabolism

Active Site

  • specific shape with active site in enzyme
  • region of enzyme where substrate will bond and reaction will occur
  • reaction will occur here
  • chemical attraction between AS and enzyme
  • enzyme and substrate is like lock and key

Denaturation

  • enzyme loses conformation and can't function
  • separate 2 DNA strands
  • extreme conditions of pH, salt concentration, and temperature cause this catalyst change reaction rate without being consumed

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Immobilized Enzymes

  • in industry
  • restrict enzyme movement
  • commercial use of 500+ enzymes
  • more stable
  • uses biotechnology

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Biotechnology

  • makes products like laundry detergent, textile preparation, biodegradable clothing

  • normal production of lactase, which breaks lactose into glucose and galactose

  • makes yeast, which makes lactase

  • helps in lactose intolerance

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3 steps in catalysis

  1. Substrate(s) bond to active site (s)
  2. Substrate turns to a product bound to the enzyme
  3. Active Site releases the product and can catalyze other substances

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Substrate Movement

  • random movement in water
  • substrate smaller and faster than enzyme
  • random movement causes collision which causes enzyme-catalyzed reaction

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Enzymes & Temperature

  • temperature increase causes enzyme efficiency to increase until a certain point

  • once that point is crossed, the enzyme denatures

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Enzymes & pH

  • optimum pH of 7
  • activity level reduced with pH change

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Enzymes & Substrate Concentration

  • directly proportional
  • until all enzymes are active
  • then no effect on concentration

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Cofactors

  • nonprotein enzyme helpers
  • inorganic or organic
  • organic includes coenzymes
  • coenzymes include vitamins

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Enzyme Inhibitors

  • slow down enzyme reaction rate
  • competitive or noncompetitive
  • ex. toxin, poison, pesticides, antibiotics

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Competitive Inhibitor

  • binds to enzyme's active site
  • directly competes with the substrate

Competitive Inhibitor Graph

  • same Vmax
  • lower Km

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Noncompetitive Inhibitor

  • binds to other part of enzyme
  • denatures it, making it less useful
  • same Km, lower Vmax

Noncompetitive Inhibitor Graph

  • same Km
  • lower Vmax

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Enzyme Regulation

  • chemical chaos if cell's metabolic pathways weren't tightly regulated
  • cells switch genes encoding certain enzymes on and off or regulating enzyme activity

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Allosteric Regulation

  • inhibit or stimulate enzyme
  • regulatory molecule binds to enzyme at one site and affects action at another

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Allosteric Regulation & Inhibition

  • most allosteric-regulated enzymes made from polypeptide subunits
  • active and inactive forms
  • activator binding and inhibitor binding

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Activator binding site

  • stabilizes the active form of the enzyme

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Inhibitor Binding Site

  • stabilizes enzyme's inactive form

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Feedback Inhibition

  • end-product of metabolic pathway shuts down the pathway
  • prevents a cell from wasting chemical resources by synthesizing extra product

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Assumption of a Steady State

  • transient phase where ES concentration does not change during the reaction (dES/dt) = 0 Km
  • substrate concentration where V0 = (1/2) (Vmax)

Enzyme classification

  • uses a number system

Enzyme Classes

  • Oxidoreductase

    • transfer electrons in Redox reactions to catalyze oxidation or reduction
    • oxidation
    • reduction in electrons
    • increase oxidation state
    • reduction
    • increase in electrons
    • decrease oxidation state
  • Transferase

    • transfer functional groups between molecules
  • Hydrolase

    • break bonds by adding H2O
  • Lyase

    • elimination reactions to form double bonds
    • remove hydrogen and carbon
  • Isomerase

    • aka utase
    • intramolecular arrangements
    • one of the "weirder" enzymes
  • Ligase

    • join molecules with new bonds metabolism
    • total of organism's chemical reactions
    • emergent property from cellular molecule interactions

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Metabolic Pathway

  • begins with a specific molecule and ends with a product
  • chain of reactions
  • enzymes catalyze each step

Catabolic pathways

  • release energy by breaking down complex molecules into simpler ones
  • ex. cellular respiration

Anabolic Pathways

  • use energy to build complex molecules from simpler ones
  • ex. protein synthesis from amino acids

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Bioenergetics

  • the study of how organisms manage their energy resources

Energy

  • the capacity to cause change
  • exists in various forms
  • some forms can perform work

Kinetic energy

  • energy associated with motion
  • Heat (thermal energy)
  • kinetic energy
    • associated with the random movement of atoms of molecules

Potential Energy

  • energy that matter possesses because of its location or structure

Chemical Energy

  • potential energy available for release in a chemical reaction

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Thermodynamics

  • the study of energy transformations

Isolated System

  • isolated from its surroundings
  • ex. liquid in a thermos

Open System

  • energy and matter can be transferred between the system and its surroundings
  • ex. organisms

First Law of Thermodynamics

  • energy of the universe is constant
  • energy can't be created or destroyed, only changed
  • principle of conservation of energy

Second Law of Thermodynamics

  • during every energy transfer or transformation, some energy is unusable, and is often lost as heat

  • each change increases the entropy (disorder) of the universe

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Spontaneous Processes

  • occur without energy input
  • they can happen quickly or slowly
  • increase entropy of the universe

Biological Order and Disorder

  • cells create ordered structures from less ordered materials
  • organisms replaced ordered forms of matter and energy with less ordered forms
  • energy flows into an ecosystem as light and out as heat

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Exergonic Reaction

  • net release of free energy
  • spontaneous

Endergonic Reaction

  • absorbs free energy from its surroundings
  • nonspontaneous

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